The present invention concerns an improvement on a double toric sealing ring analogous to the one described in French Pat. No. 2,398,940, filed on July 26, 1977. It is constructed of two toric sealing ring structures interconnected by a resilient membrane. The two sealing ring structures, one ensures a static seal and the other a dynamic seal, produce an upstream/downstream seal in a valve.
The double toric sealing ring comprises a counter ring mounted on the toric sealing ring structure that ensures a dynamic seal. In particular, the counter ring absorbs the compression forces at the valve seat, for example, at a groove in a butterfly closure member in the case of a butterfly valve, and equally distributes contact pressure along the circumference (thereby resulting in self-centering of the sealing ring structure). This counter ring is mounted radially on the sealing ring structure to ensure a dynamic seal, and floats with it to allow self-centering of the sealing ring structure on the sealing surface of the butterfly closure member.
In the embodiment described in the French Pat. No. 2,398,940, the aforesaid flexible membrane consists of a toric part whose section of revolution has a general C shape, the ends of which wrap around the two sealing ring structures, and a middle section which has a V-shaped fold. The two sealing ring structures are tangentially located on opposite sides of the V-shaped fold.
The precedingly defined double ring obtains excellent results, particularly in the case of shut-off valves, such as butterfly valves.
In this last application, the double ring is placed in an annular cavity formed between the side face of the butterfly valve body and a flange attached to the side by bolts. This cavity opens into the inner chamber of the valve body.
The base of the cavity comprises an annular groove formed by a step of the bore of the flange and by the side face of the valve body. This groove receives the first toric sealing ring structure and combines with it to form a first static seal, the sealing pressure being obtained by the tightening of the aforesaid flange on the valve body by means of the aforesaid bolts.
On the side face of the valve body is a circular groove in which the V-shaped fold of the aforesaid membrane is positioned.
Such an arrangement notably requires on one part, the formation of a relatively complex flange, fixed on the valve body, and on the other part, machine finishing of the side face of the valve.